In recent years, sputtering methods have been widely used for deposition of metal layers or insulating layers in the manufacturing fields of semiconductor apparatuses, solar cells, and electronic devices using FPD (Flat Panel Display) and MEMS (Micro-Electro-Mechanical Systems) techniques. In a sputtering method, plasma is formed in a vacuum chamber in which a target formed of a deposition material and a substrate are opposed to each other, and sputtering particles from the target that are generated by causing ions in plasma to come into collision with the target are deposited on the substrate, to thereby form a film.
Stable sputtering of a target and a film quality of a thin film to be formed depend on the quality of a target to be used to a large extent. Specifically, a sputtering target is required to have high relative density, a uniform composition, fine crystal grains, and the like. For example, in the manufacturing of a metal target, an ingot formed of crystalline metal is subjected to machining such as rolling or forging, thus obtaining the characteristics described above.
For example, Patent Document 1 discloses a method of manufacturing an aluminum alloy sputtering target, in which an ingot as an alloy of aluminum and copper is subjected to cold working and the working material is rapidly cooled after being annealed at a predetermined temperature in a flow of argon.
Further, Patent Document 2 discloses a method of manufacturing a cobalt target for sputtering, in which a cobalt ingot is subjected to hot forging and hot rolling to produce a plate material, the thickness of the plate material is made uniform, and then a cold rolling process in biaxial directions at the same rolling ratio and a heat treatment process at a predetermined temperature are repeated.
Patent Document 1: Japanese Patent Application Laid-open No. 2002-69626 (paragraph [0006])
Patent Document 2: Japanese Patent Application Laid-open No. 2007-297679 (paragraph [0015])